date regex

Plankton has asked for the wisdom of the Perl Monks concerning the following question:

Friends,

I almost have what I think would work as a date regex. But I don't think that a regex will be able to catch bad dates like 1968-04-31, April 31st 1968.

#!/usr/local/bin/perl -w
use strict;
 
# CCYY-MM-DD[tz]
my $pat = qr /^-?\d{4,}-(0\d|1[0-2])-\d\d(Z?|([+|-]{0,1}[0-2]?\d:[0-5]
+\d)?)$/;
while (<DATA>) {
    chomp;
    print "$_ ", /$pat/ ? "matches\n" : "does not match\n";
}
 
__DATA__
1968-04-02
-0045-01-01
11968-04-02
1968-04-02+05:00
1968-04-02Z
invalids to follow
68-04-02
1968-4-2
1968/04/02
04-02-1968
1968-04-31
[download]

Output

bash-2.03$ ./date_regex.pl 
1968-04-02 matches
-0045-01-01 matches
11968-04-02 matches
1968-04-02+05:00 matches
1968-04-02Z matches
invalids to follow does not match
68-04-02 does not match
1968-4-2 does not match
1968/04/02 does not match
04-02-1968 does not match
1968-04-31 matches
[download]

Plankton: 1% Evil, 99% Hot Gas.

Comment on date regex Select or Download Code

Replies are listed 'Best First'.
Re: date regex Can this be done? by Ovid (Cardinal) on Oct 13, 2003 at 19:33 UTC
Use the `(??{})` construct and it's pretty easy: #!/usr/local/bin/perl use warnings; use strict; use Date::Simple; $\|++; my $good_date = sub { my ($year,$month,$day) = ($1, $2, $3); my $date = do { no warnings 'uninitialized'; Date::Simple->new($year,$month,$day) }; return $date ? qr{(?=)} : qr{(?!)}; }; # CCYY-MM-DD[tz] my $pat = qr /^(\d\d\d\d)-(\d\d)-(\d\d)(??{$good_date->()})/; while (<DATA>) { chomp; print "$_ ", /$pat/ ? "matches\n" : "does not match\n"; } __DATA__ 1968-04-02 -0045-01-01 11968-04-02 1968-04-02+05:00 1968-04-02Z invalids to follow 68-04-02 1968-4-2 1968/04/02 04-02-1968 1968-04-31 [download] And the output: `1968-04-02 matches -0045-01-01 does not match 11968-04-02 does not match 1968-04-02+05:00 matches 1968-04-02Z matches invalids to follow does not match 68-04-02 does not match 1968-4-2 does not match 1968/04/02 does not match 04-02-1968 does not match 1968-04-31 does not match` I gave a simplified example to show you how it's done, but you'll want to flesh out that regex more. Cheers, Ovid New address of my CGI Course.	[reply] [d/l]
Re: date regex Can this be done? by hardburn (Abbot) on Oct 13, 2003 at 19:22 UTC
Anything can be done in a regex if you use `/e`, `?{ }`, or `??{ }`. I just don't promise it will be easy :) If you want easy, look at Date::Manip or one of the other multitude of Date/Time modules on CPAN. ---- I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident. -- Schemer Note: All code is untested, unless otherwise stated	[reply] [d/l] [select]